1. Field of the Invention
The present invention relates generally to horizontal bandsaw machines having a flexible endless bandsaw blade trained around a plurality of wheels or pulleys to perform cutting operations and, more particularly, pertains to guide means for guiding the bandsaw blade according to sizes and shapes of workpieces to be cut in the horizontal bandsaw machines.
2. Description of the Prior Art
As is well known, horizontal bandsaw machines comprise a base on which a workpiece or workpieces to be cut are to be placed and clamped and a saw head assembly in which a flexible endless bandsaw blade is trained around a pair of wheels or pulleys, one of which is power driven to drive the bandsaw blade. In the saw head assembly, the bandsaw blade is slidably held and guided with its cutting edge faced perpendicularly downwardly by a pair of guide means at the cutting zone where cutting is performed so that it may cut into the workpiece to be cut. Either or each of the guide means is arranged to be adjustably moved toward and away from the other to adjust the cutting stretch of the bandsaw blade at the cutting zone according to sizes of the workpieces to be cut, and auxiliary guide means are often provided to supplement the main guide means. Also, the saw head assembly is so arranged as to be raised away from and lowered toward the base by a suitable means such as a hydraulic motor around a hinge pin or along one or more vertically disposed guide means. Thus, in each cutting cycle, the saw head assembly is firstly raised and then lowered towards the base so as to enable the bandsaw blade being driven therein around the wheels to cut the workpiece which has been placed and clamped on the base. Also, in automatic horizontal bandsaw machines, there are provided arrangements for automatically raising and lowering the saw head assembly and automatically feeding workpieces to be cut into the cutting zone after completion of each cutting cycle.
In the horizontal bandsaw machine of the above described arrangement, it is desired to make the span or distance between the guide means for guiding the bandsaw blade as short as possible in order to increase the cutting accuracy and lengthen the life of the bandsaw blade and also minimize the noise occurring during a cutting operation. When the distance between the guide means for the bandsaw blade is too long, the bandsaw blade will have a tendency to be upwardly buckled or bent because of the feeding pressure during a cutting operation and also it will be severely vibrated upwardly and sidewardly. In other words, the longer the distance between the guide means for the bandsaw blade is made, the more the bandsaw blade will be upwardly buckled or bent and severely vibrated during a cutting operation. Also, when the bandsaw blade is upwardly buckled or bent during a cutting operation, its cutting edge will have a tendency to be directed not perpendicularly but aslant to the workpieces to be cut, and as the result the bandsaw blade will laterally deviate or vary out from the desired line of cut to be made on the workpiece. Of course, the bandsaw blade deviating from its proper course will not be able to perform an accurate cutting operation and also it will be undesirably worn and broken very often. Also, the vibration of the bandsaw blade will not only increase the noise during a cutting operation but also it will result in poor cutting accuracy and short life of the bandsaw blade.
In the conventional horizontal bandsaw machines, the distance between the guide means for guiding the bandsaw blade is adjusted so as to be made as short as possible according to the largest cross-sectional portion of the workpiece to be cut. More particularly, either of the guide means that is adjustably movable is set to the nearest position possible to the other in a manner such that the bandsaw blade can cut the largest cross-sectional portion of the workpiece to be cut in the conventional horizontal bandsaw machines. Also, the distance between the guide means in the conventional horizontal bandsaw machines is not changed but is kept fixed during a cutting cycle after it is initially set according to the largest cross-sectional length of the workpiece to be cut. Accordingly, the distance between the guide means adjusted to be set according to the largest cross-sectional length of the workpiece to be cut is too long when the bandsaw blade is cutting the smaller cross-sectional portion of the workpiece in the conventional horizontal bandsaw machines. Since the cross-sectional length of the workpiece to be cut varies as the bandsaw blade goes on cutting the workpiece, no really satisfactory cutting can be expected with the distance between the guide means fixedly set to the largest cross-sectional length of the workpiece to be cut. Thus, the cutting accuracy cannot be increased to the highest degree, nor can the life of the bandsaw blade be lengthened to the utmost, nor can the noise be satisfactorily minimized in the conventional horizontal bandsaw machines.
On the other hand, it is desired to automatically adjust the distance between the guide means for the bandsaw blade especially for the purpose of laborsaving and unattended cutting operations in the horizontal bandsaw machines. In the conventional horizontal bandsaw machines, either of the guide means is manually moved toward and away from the other and then manually fixed at a desired position in order to adjust the distance between the guide means, each time when it is desired to cut a workpiece or workpieces of a different size. Accordingly, heretofore, it has been very troublesome to adjust the distance between the guide means, and also it has been impossible to automatically continuously cut workpieces varied in size under unattended operations. Since it has been possible to automatically and continuously feed, clamp and cut workpieces in the conventional horizontal bandsaw machines, it has been desired to automatically adjust the distance between the guide means for the bandsaw blade to automatically continuously cut a variety of workpieces.